Yes, Danny is sharing his decades of experience, R&D, products, simply amazing. We are very fortunate to have people like this in our industry helping us to leverage and improve on our existing investments. When it works well, he makes money $ at it! And, saving $ YOU money too if you can upgrade your speakers.
Positive Feedback on GR/Danny:
A close friend who does not post here is a very happy customer, recently. I was involved in the self-help project some. After getting the woofer surrounds and voice coils re-done in the mid woofers, he sent in one of his Vienna Acoustics speakers (recently); its on the recent videos where Danny was "confused, perplexed" by the measured speaker as-is while comparing two VA speaker units from two different customers. Danny was transparent. It was not a trap set by us, we just did not say much, wanted to see what would happen.
What Danny did not know is the speaker my friend sent in was recently upgraded, caps, and more. It was a cheap uplift i/we did to the stock crossover, and better than the stock crossovers, but not the best yet. I could not get my buddy to buy even better parts. It was an experiment with mildly more expensive parts over stock. Not the max, went from $10 caps to $20 caps at best on try-1. Buddy was happy with the midway lift from cheap parts to mid-fi parts for a minute. That lasted for a few months then it made him think more, "..what about even better parts and even better design - can these speakers sound even better ???". Time to step it up, again, he paid the $ to box and ship one heavy speaker to Danny.
My buddy wanted MORE, wanted hi-fi grade parts and redesign, so he sent it to Danny at GR Research. Danny ended up measuring and redesigning the whole approach and transformed the stock crossover from a 2.5 way design to a true 3-way design; thus using one woofer for lower bass and the other woofer for mid bass range, the tweeter frequency changed some too. Frequency response looks good, some of the odd peaks and crazy dips were smoothed out a LOT. Danny provides all the parts in the kit, wiring too if needed. Buddy had to assemble the crossover, soldering it together. This is something to be aware of and ask about.
Results:
"Sounds much better, more transparent", "more musical" to my friend. His "wife noticed a difference too". He uses the revised VA Grand speakers with a Black Ice Audio F22 tube amp and says they "not only sound better but have more output for whatever reason". This surprised me. There you go. Buddy saved about $6-7k on other speakers he was looking at before. Not now, he's done! No need, the upgrade worked in a positive way.
re: Danny / GR Research -
Yes, Danny is trying to sell kits. That's what he's in business to do and does a pretty good job at it.
Note: Your results may vary and low cost speakers with cheap low grade woofers and tweeters may not benefit as much. First hand feedback helps I hope. There ya go.